docs: def get_ratefactor(self, base, code):
          """Return the Decimal currency exchange rate factor of 'code' compared to 1 'base' unit, or RuntimeError"""
          self.get_latestcurrencyrates(base)
          try:
              ratefactor = self.rates["rates"][code]
          except KeyError:
              raise RuntimeError("%s: %s not found" % (self.name, code))
  
          if base == self.base:
              return ratefactor
          else:
              return self.ratechangebase(ratefactor, self.base, base)